Is Taiwan developed?

If by developed, you mean a second world country, then yes, Taiwan is developed. Although they do not receive as much income per year as Americans do, the cost of living there is very low (I bought 20 t-shirts for only 60 USD, and they were pretty good quality).

Taiwan is one of the four Asian Tigers and it is classified as a highly advance country/economy by the IMF and the World Bank. Taiwan produces quite a large portion of the world technology and they are most known for their advance computer chips.